1. Field of the invention
The present invention relates to a plate-type refrigerant evaporator especially used for an air-conditioner of automobile.
2. Description of the Prior Art
A conventional plate-type evaporator has a plurality of tubes each of which is formed by joining a pair of core plates so as to form a seal. An inlet tank portion and an outlet tank portion are also formed in the core plates.
FIG. 6 shows the core plate 100. The core plate 100 has an inlet tank portion 120 for forming an inlet tank, and an outlet tank portion 130 for forming an outlet tank. A fluid passage 110 for forming the tube is U-shaped. One end of the fluid passage 110 is connected to the inlet tank portion 120 through an inlet portion 111 and the other end is connected to the outlet tank portion 130 through an outlet portion 112.
A cross sectional area of the fluid passage 110 is constant from the inlet portion 111 to the outlet portion 112.
A large amount of a liquid-phase refrigerant which has small specific volume is introduced into the fluid passage 110 through the inlet portion 111. The introduced liquid-phase refrigerant evaporates into a gas-phase refrigerant which has large specific volume while it flows in the fluid passage 110 toward the outlet portion 112, so that the flowing velocity of the refrigerant is increased and a pressure loss of the refrigerant is increased as the refrigerant flows toward the outlet portion 112.